A protestor holds his cell phone as he faces off with sheriffs during demonstrations against the shooting of Jacob Blake in Kenosha, Wisconsin on Tuesday. — AFP/VNA Photo

KENOSHA — A 17-year-old was arrested on murder charges Wednesday after two people were shot dead during demonstrations against police brutality in the US city of Kenosha, as authorities released their first account of the shooting of a black man by an officer that ignited the violence.

Outrage continued to spread after Kenosha, Wisconsin police shot Jacob Blake multiple times in the back point-blank in front of his children in the Midwestern city last Sunday.

As President Donald Trump vowed to send in federal forces, the NBA cancelled all three playoff games Wednesday after the Milwaukee Bucks – whose home base is just to the north of Kenosha – boycotted their game in protest at Blake's shooting.

"We're tired of the killings and the injustice," Bucks player George Hill was quoted by The Undefeated website as saying.

The boycott also spread to baseball, with the Milwaukee Brewers refusing to play their Major League Baseball game against the Cincinnati Reds on Wednesday, according to US media.

After days of silence, Wisconsin authorities released their first statement Wednesday on what happened in the moments before the shooting, saying Blake had a knife "in his possession" when Officer Rusten Sheskey, a seven-year veteran of the force, fired his gun seven times into the 29-year-old's back.

It was not clear from the statement if the knife, recovered from inside the car, was in Blake's hands when he was shot or at any other point during the altercation.

Kenosha city officials ordered a 7:00 pm to 7:00 am curfew through Sunday in hopes of bringing calm after Tuesday's violence, which occurred as mostly white armed vigilantes flocked to the site of protests, saying they were there to defend private property.

Videos taken overnight Tuesday show one of the vigilantes shooting at protesters with an assault rifle and apparently hitting two who tried to stop him.

The man then walks down the street freely, gun slung across his chest, while protesters scatter and police vehicles drive past him.

Two men were killed and one wounded in the arm in the shooting.

Police in Antioch, Illinois, about 20 miles (32 kilometers) southwest of Kenosha, announced Wednesday afternoon that they had arrested a 17-year-old wanted in Kenosha for murder.

The suspect is widely identified as Kyle Rittenhouse.

Antioch court records indicate that Rittenhouse had been arrested as a fugitive on Wednesday and would face a hearing on his extradition to Wisconsin on Saturday.

'Restore law and order'

Blake remained hospitalized Wednesday and may be permanently paralyzed from the waist down, according to his family.

Kenosha city police chief Daniel Miskins appeared before the media for the first time since Sunday but refused to answer questions on Blake's shooting.

However, the Wisconsin Department of Justice released a statement later that gave the official side of the incident for the first time.

Officers were sent to a residence in Kenosha "after a female caller reported that her boyfriend was present and was not supposed to be on the premises," the statement said.

During the incident, officers "attempted to arrest" Blake, it continued.

"Law enforcement deployed a taser to attempt to stop Mr Blake, however the taser was not successful in stopping Mr Blake. Mr Blake walked around his vehicle, opened the driver's side door, and leaned forward. While holding onto Mr Blake's shirt, Officer Rusten Sheskey fired his service weapon 7 times.

Officer Sheskey fired the weapon into Mr Blake's back," it said.

"During the investigation following the initial incident, Mr Blake admitted that he had a knife in his possession," the statement said, adding that agents "recovered a knife from the driver's side floorboard of Mr Blake's vehicle."

Bystander video shows Sheskey shooting Blake as he tried to enter his car, which held his three sons, after what various witnesses describe as his intervention in a domestic incident.

Blake's father Jacob Blake Sr accused police of "senseless attempted murder."

'Find another way'

Blake's mother Julia Jackson pleaded for an end to the violence.

"For anyone who is doing anything that is violent or destructive, please stop," she said in an interview Wednesday with ABC News.

"I get your pain. I get your frustration. This is nothing new and it's not just about my son, I get that. But please find another way."

Meanwhile, US President Donald Trump announced he was deploying federal law enforcement and national guard troops to Kenosha "to restore law and order."

"We will NOT stand for looting, arson, violence, and lawlessness on American streets," Trump tweeted.

But local officials said they already had hundreds of police from around the state, some 250 national guard troops, and FBI and federal marshals helping them with the situation.

Trump's comments made clear the violence would also be fodder for the ongoing presidential race, with the election just over two months away.

His campaign has portrayed anti-police protests in numerous cities as an extreme leftist threat to the country.

Democratic rival Joe Biden called for an end to violence after Blake's shooting.

"Once again, a Black man – Jacob Blake – was shot by the police. In front of his children. It makes me sick," Biden tweeted Wednesday.

"Is this the country we want to be? Needless violence won't heal us. We need to end the violence – and peacefully come together to demand justice," he wrote. — AFP